This paper presents a new patented technique for gathering and delivering produced fluids from the laterals of horizontal wells to a centralized production facility to address the following challenges. First, decreasing the velocities of produced fluids results in accumulation of proppant and fractured rock particles in the production liner or casing. The inflow rate is zero within the production intervals located between the toe of the well and the plugged section closest its heel. Second, placing the sucker-rod pump closer to the lateral eventually makes the well operation unprofitable due to a high well failure frequency caused by the wellbore deviation. Third, wax and paraffin deposition in the flowlines adds the cost of hot oiling or watering to the total operating expenses.
Each well is outfitted with a Multiphase Pumping System for Artificial Lift (MAPS-AL) and a flushing system for flowlines. MAPS-AL lifts the liquids from the heel section to the rod pump installed in the vertical section of the well and removes solids and paraffin wax build-up out of the tubing, pump, and rod (i.e., performs automatic hot watering). The flushing system generates fluid batches (predetermined fluid volumes) to prevent paraffin deposition in the flowline. Transient 3-phase gas-oil-water flow simulations were carried out to study performance of the artificial lift and oil gathering systems. The transient high-fidelity model of the flow used for simulations is capable of predicting simultaneously gas-liquid flow pattern and oil-water flow pattern in the liquid phase.
The fluid batches periodically increase the local free-water and oil velocities several times both in the lateral and the flowline. Cycling variations of local free-water velocity convert stationary solids beds into slowly moving dunes. Free-water residence time in the entire system is reduced. The artificial lift system cyclically accelerates the flow of produced liquids in the heel section to deliver them into the pump intake. Each free-water batch enters the flowline during approximately 2 min and then is moved by the production stream toward the 1st stage separator, like a mechanical pig. This enables operators to consolidate numerous oil and gas processing facilities, typically located at or within 1/2 mile of multi-well pads, into one centralized production facility.
The proposed technique enabled operators to reduce the frequency of sucker-rod-pumping failures (failures of all components-the pump, tubing, and rod) related to placing the pump within the heel section. The average annual pulling and equipment replacement cost can be as high as $140,000 when the pump is located in a deviated section of the well. It allows for the use of longer multiphase flowlines (over 3 mi). Also, the new way of transporting produced fluids helps operators avoid problems caused by paraffin deposition both in the well and the flowline. The artificial lift system can be engineered to lower gradually the flowing bottomhole flowing pressure to minimize the rate of increase of the gas–oil ratio and increase the oil recovery (EUR) by 50% in some cases.
